Formation of a two-layer via structure to mitigate damage to a display device

ABSTRACT

In some embodiments, the present disclosure relates to a display device that includes an isolation structure disposed over a reflector electrode, a transparent electrode disposed over the isolation structure, an optical emitter structure disposed over the transparent electrode, and a via structure. The via structure extends from the transparent electrode at a top surface of the isolation structure to a top surface of the reflector electrode. The via structure includes a center horizontal segment that contacts the top surface of the reflector electrode, a sidewall vertical segment that contacts an inner sidewall of the isolation structure, and an upper horizontal segment that is connected to the center horizontal segment by the sidewall vertical segment. The upper horizontal segment is thicker than the center horizontal segment.

BACKGROUND

Many modern day electronic devices, such as televisions and cellulardevices, use image display devices to convert digital data into opticalimages. To achieve this, the image display device may comprise an arrayof pixel regions. Each pixel region may have an optical emitterstructure and may be coupled to a semiconductor device. Thesemiconductor device may selectively apply an electrical signal (e.g., avoltage) to the optical emitter structure. Upon application of theelectrical signal, the optical emitter structure may emit an opticalsignal (e.g., light). The optical emitter structure may, for example, bean organic light emitting diode (OLED) or some other suitable lightemitting device.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIGS. 1A and 1B illustrate cross-sectional views of some embodiments ofa display device having a via structure extending through an isolationstructure, the via structure having an upper horizontal segment that isthicker than a center horizontal segment.

FIG. 2 illustrates a cross-sectional view of some additional embodimentsof a display device having a via structure comprising two layers andextending through an isolation structure, as well as example light pathsthrough different thicknesses of the isolation structure.

FIGS. 3-12 illustrate cross-sectional views of some embodiments of amethod of forming a display device having a via structure that extendsthrough an isolation structure, wherein the via structure comprises aprotective layer and a conductive layer to prevent damage to theisolation structure.

FIG. 13 illustrates a flow diagram of some embodiments of a methodcorresponding to FIGS. 3-12.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components and arrangements are describedbelow to simplify the present disclosure. These are, of course, merelyexamples and are not intended to be limiting. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

A display device includes an array of pixel regions, wherein each pixelregion comprises an isolation structure arranged between a reflectorelectrode and a transparent electrode. A via structure may extendthrough the thickness of the isolation structure and electrically couplethe reflector electrode to the transparent electrode. An optical emitterstructure may be arranged over the transparent electrode. The isolationstructure may comprise silicon dioxide having a thickness thatcorresponds to a certain color. For example, during operation of thedisplay device, an electrical signal (e.g., voltage) may be applied tothe transparent electrode from circuitry coupled to the reflectorelectrode, the via structure, and the transparent electrode. Theelectrical signal may cause light to be produced at the interfacebetween the optical emitter structure and the transparent electrode(e.g., due to electron-hole recombination). The light may reflect off atop surface of the isolation structure and/or may travel through theisolation structure, reflect off of the reflector electrode, and travelback towards the top surface of the isolation structure. Due toconstructive and/or destructive interference of a given wavelength oflight at the top surface of the isolation structure, colored lightaccording to the thickness of the isolation structure may be emittedfrom a top surface of the optical emitter structure.

To form the via structure, the isolation structure may, for example, beformed over the reflector electrode, and an opening in the isolationstructure is formed to expose a first surface of the reflectorelectrode. The opening may be formed using an etching process, whichleaves behind residue (e.g., a metal oxide) on the first surface of thereflector electrode. Thus, a cleaning process, such as an argonsputtering process, is conducted to remove the residue from the firstsurface of the reflector electrode. Absent the cleaning process,electrical contact between the via structure and the first surface maybe poor (e.g., contact resistance may be high). However, the cleaningprocess damages (e.g., increases the surface roughness) upper surfacesof the isolation structure. Because the upper surfaces of the isolationstructure receive and reflect light, when the upper surfaces of theisolation structure are damaged, the light may scatter, which may causethe emitted light to be a different color and/or reduce the intensity ofthe emitted light, for example. Thus, the cleaning process may result inan unreliable display device.

Various embodiments of the present disclosure are directed towards amethod of forming a via structure comprising a protective layer and aconductive layer on an isolation structure to prevent damage to theisolation structure of a display device. In some embodiments, aprotective layer is deposited over an isolation structure on a reflectorelectrode, such that the protective layer directly contacts top surfacesof the isolation structure. A first etching process may be performed toform a first opening in the protective layer and the isolation structureto expose a first surface of the reflector electrode. A cleaning processmay be performed to remove any residue on the first surface of thereflector electrode. Then, a conductive layer is deposited over theprotective layer, on sidewalls of the first opening defined by innersidewalls of the isolation structure, and on the first surface of thereflector electrode. A second etching process may be performed to removeperipheral portions of the protective layer and the conductive layer toform a via structure. The via structure comprises a center segmentdirectly contacting the reflector electrode, a sidewall segmentconnected to the center segment and extending upwards towards the topsurfaces of the isolation structure, and an upper horizontal segmentconnected to the sidewall segment and directly contacting the topsurfaces of the isolation structure. The horizontal segment comprisesthe protective layer and the conductive layer, and thus, the horizontalsegment may be thicker than the center segment. Because of thedeposition of the protective layer on the isolation structure, the topsurfaces of the isolation structure are protected during the cleaningprocess, damage to the top surfaces of the isolation structure ismitigated, and a reliable display device may be produced.

FIG. 1A illustrates a cross-sectional view 100A of some embodiments of adisplay device comprising via structures extending through an isolationstructure.

The display device of the cross-sectional view 100A includes a firstpixel region 101 a, a second pixel region 101 b, and a third pixelregion 101 c. Each of the first, second, and third pixel regions 101 a,101 b, 101 c are configured to emit a different color of light (e.g.,red, green, blue) when subjected to an electrical signal (e.g.,voltage), and the color of light depends on the thickness of theisolation structure 106. For example, in some embodiments, the firstpixel region 101 a may comprise a first portion 106 a of the isolationstructure 106 that has a first thickness t₁; the second pixel region 101b may comprise a second portion 106 b of the isolation structure 106that has a second thickness t₂; and the third pixel region 101 c maycomprise a third portion 106 c of the isolation structure 106 that has athird thickness t₃. In some embodiments, the first, second, and thirdthicknesses t₁, t₂, t₃ are each different from one another. For example,in some embodiments, the first thickness t₁ may be greater than thesecond and third thicknesses t₂, t₃, and the second thickness t₂ may begreater than the third thickness t₃. In some embodiments, the isolationstructure 106 may comprise an oxide (e.g., silicon dioxide), a nitride(e.g., silicon nitride), or some other material that has opticalproperties, such that incident light may reflect as a colored light dueto constructive and/or destructive interference, and wherein the colorof the colored light is dependent on the thickness of the isolationstructure 106. For example, the first thickness t₁ may correspond togreen light; the second thickness t₂ may correspond to blue light; andthe third thickness t₃ may correspond to red light.

In some embodiments, the isolation structure 106 is arranged between areflector electrode 102 and a transparent electrode 112. First barrierstructures 104 may be arranged between portions of the reflectorelectrode 102 such that each pixel region 101 a, 101 b, 101 c comprisesan electrically isolated portion of the reflector electrode 102. In someembodiments, an optical emitter structure 110 may be arranged over thetransparent electrode 112. Further, in some embodiments, second barrierstructures 114 may be arranged over the isolation structure 106 andbetween portions of the optical emitter structure 110 and thetransparent electrode 112 to isolate the first, second, and third pixelregions 101 a, 101 b, 101 c from one another.

In some embodiments, the reflector electrode 102 may be coupled tocontrol circuitry 120. For example, in some embodiments, the reflectorelectrode 102 is disposed over an interconnect structure 130 comprisinga network of interconnect wires 134 and interconnect vias 136 embeddedin an interconnect dielectric structure 132. In some embodiments, theinterconnect structure 130 is arranged over a substrate 122 and coupledto semiconductor devices 124. In some embodiments, the semiconductordevices 124 may be, for example, metal oxide semiconductor field-effecttransistors (MOSFETs) comprising source/drain regions 124 a within thesubstrate 122 and a gate electrode 124 b over the substrate 122. Thegate electrode 124 b may be separated from the substrate 122 by a gatedielectric layer 124 c. The control circuitry 120 is configured toselectively supply an electrical signal (e.g., voltage) to each of thefirst, second, and third pixel regions 101 a, 101 b, 101 c to emitcolored light as indicated by digital data.

In some embodiments, each of the first, second, and third pixel regions101 a, 101 b, 101 c comprises a via structure 108 such that theelectrical signal (e.g., voltage) may be supplied to the transparentelectrode 112 and the optical emitter structure 110. The electricalsignal (e.g., voltage) may, for example, cause electron-holerecombination between the transparent electrode 112 and the opticalemitter structure 110 that produces light, and that light may reflectoff of top surfaces of the isolation structure 106 and/or travel throughthe isolation structure 106, reflect off of the reflector electrode 102and exit through the top surfaces of the isolation structure 106. Due toconstructive and/or destructive interference, colored light dependent onthe thickness of the isolation structure 106 is emitted.

In some embodiments, the via structure 108 extends from a top surface106 t of the isolation structure 106 and extends down towards a firstsurface 102 f of the reflector electrode 102, thereby electricallycoupling the reflector electrode 102 to the transparent electrode 112.The first surface 102 f of the reflector electrode 102 may be a topsurface of the reflector electrode 102. In some embodiments, the viastructure 108 has a fourth thickness t₄ along the first surface 102 f ofthe reflector electrode, and the via structure 108 has a fifth thicknesst₅ along the top surface 106 t of the isolation structure 106. In someembodiments, the fifth thickness t₅ is greater than the fourth thicknesst₄ because the via structure 108 may include multiple layers (see, FIG.1B) along the top surface 106 t of the isolation structure 106 as aresult of protecting the top surface 106 t of the isolation structure106 during manufacturing of the via structure 108 to produce a reliabledisplay device.

FIG. 1B illustrates a cross-sectional view 100B of some embodimentscorresponding to box B of FIG. 1A.

In some embodiments, the via structure 108 may be described ascomprising a center horizontal segment 108 c contacting the firstsurface 102 f of the reflector electrode 102, a sidewall verticalsegment 108 s contacting an inner sidewall 106 s of the isolationstructure 106, and an upper horizontal segment 108 u contacting the topsurface 106 t of the isolation structure 106, wherein the sidewallvertical segment 108 s connects the upper horizontal segment 108 u tothe center horizontal segment 108 c. In some embodiments, from thecross-sectional view 100B, there are two upper horizontal segments 108 useparated from one another by the transparent electrode 112, and thereare two sidewall vertical segments 108 s separated from one another bythe transparent electrode 112. In some embodiments, the upper horizontalsegment 108 u comprises a conductive layer 108 b over a protective layer108 a, and the sidewall vertical segment 108 s and the center horizontalsegment 108 c comprise the conductive layer 108 b and not the protectivelayer 108 a.

In some embodiments, the protective layer 108 a and the conductive layer108 b may each comprise a conductive material. In alternativeembodiments, the protective layer 108 a is a dielectric materialdifferent than the isolation structure 106 instead of a conductivemetal. However, this may degrade electrical coupling to the transparentelectrode 112 at sidewalls of the via structure 108. In someembodiments, the protective layer 108 a and the conductive layer 108 bcomprise a same conductive material, whereas in other embodiments, theprotective layer 108 a and the conductive layer 108 b may comprisedifferent conductive materials. For example, in some embodiments, theprotective layer 108 a and the conductive layer 108 b may comprise asame material, such as titanium nitride. Thus, in some embodiments, theprotective layer 108 a and the conductive layer 108 b may not bedistinguishable from one another. However, the presence of theprotective layer 108 a may be detected because the upper horizontalsegment 108 u has a fifth thickness t₅ that is greater than a fourththickness t₄ of the center horizontal segment 108 c. In someembodiments, the fourth thickness t₄ may be described as a measurementfrom a bottommost surface of the via structure 108 to a bottommostsurface of the transparent electrode 112.

Similarly, in some embodiments, the fifth thickness t₅ may be describedas a measurement from the top surface 106 t of the isolation structure106 to a topmost surface of the via structure 108. In some embodiments,the fourth thickness t₄ is measured in a first direction normal to thefirst surface 102 f of the reflector electrode 102, and the fifththickness t₅ is also measured in the first direction. A differencebetween the fifth thickness t₅ and the fourth thickness t₄ may be equalto a thickness of the protective layer 108 a. Further, the sidewallvertical segment 108 s may have a sixth thickness t₆ measured in asecond direction that is perpendicular to the first direction. In someembodiments, the sixth thickness t₆ may be described as a measurementbetween an inner sidewall 106 s of the isolation structure 106 and aninner sidewall of the transparent electrode 112. In some embodiments,the fifth thickness t₅ is greater than each of the fourth thickness t₄and the sixth thickness t₆. Further, in some embodiments, the fourththickness t₄ is about equal to the sixth thickness t₆.

In some embodiments, the fourth thickness t₄ and the sixth thickness t₆may each be in a range of between, for example, approximately 200angstroms and approximately 700 angstroms. In some embodiments, thefifth thickness t₅ may be in a range of between, for example, 300angstroms and approximately 1000 angstroms. Thus, in some embodiments, adifference between the fourth and fifth thicknesses t₄, t₅ may be atleast equal to 100 angstroms. Further, in some embodiments, a ratio ofthe fifth thickness t₅ to the fourth thickness t₄ may be at least equalto approximately 1.15.

FIG. 2 illustrates a cross-sectional view 200 of some embodiments of adisplay device comprising via structure extending through an isolationstructure and various light paths during operation of the displaydevice.

In some embodiments, the via structure 108 may completely andcontinuously fill the space laterally between the inner sidewalls 106 sof the isolation structure 106 in each pixel region (101 a, 101 b, 101c). In such embodiments, the via structure 108 may still comprise theprotective layer 108 a and the conductive layer 108 b. Further, in someembodiments, the conductive layer 108 b may extend from above the topsurfaces 106 t of the isolation structure 106 and to a top surface 102 tof the reflector electrode 102, whereas the protective layer 108 a maydirectly contact and be arranged on the top surfaces 106 t of theisolation structure 106. The protective layer 108 a does not extendbelow the top surfaces 106 t of the isolation structure 106.

In some embodiments, the first pixel region 101 a, the second pixelregion 101 b, and the third pixel region 101 c each comprise a reflectorelectrode (102 of FIG. 1A) having substantially equal widths. However,in other embodiments, as in the cross-sectional view 200 of FIG. 2, thefirst pixel region 101 a may have a first reflector electrode portion102 a having a first width w₁; the second pixel region 101 b may have asecond reflector electrode portion 102 b having a second width w₂; andthe third pixel region 101 c may have a third reflector electrodeportion 102 c having a third width w₃. In such embodiments, the first,second, and third widths w₁, w₂, w₃ may be different from one another.For example, in some embodiments, the third width w₃ may be smaller thanthe second width w₂, and the second width w₂ may be smaller than thefirst width w₁. In some embodiments, the smallest width (e.g., w₃)corresponds to the pixel region (e.g., 101 c) that has a portion of anisolation structure 106 with a smallest thickness (e.g., t₃). Similarly,in some embodiments, the largest width (e.g., w₁) corresponds to thepixel region (e.g., 101 a) that has a portion of an isolation structure106 with a smallest thickness (e.g., t₁). However, in other embodiments,the relationship between widths of the reflector electrode 102 does nothave a correlation with the thicknesses of the isolation structure 106.

The cross-sectional view 200 illustrates an exemplary first light path202 in the second pixel region 101 b and an exemplary second light path204 in the third pixel region 101 c. In some embodiments, light isgenerated at a first interface 206 between the optical emitter structure110 and the transparent electrode 112 due to an electrical signal (e.g.,voltage) applied to the reflector electrode 102 by the control circuitry120. For example, in the cross-sectional view 200, the second pixelregion 101 b and the third pixel region 101 c are “ON” (e.g., light isgenerated at the first interface 206), whereas the first pixel region101 a is “OFF” (e.g., light is not generated at the first interface206). In the second pixel region 101 b, the exemplary first light path202 shows how in some embodiments, the generated light at the firstinterface 206 may reflect off of the top surface 106 t of the secondportion 106 b of the isolation structure 106 and/or travel through thesecond portion 106 b of the isolation structure 106, reflect off of thesecond reflector electrode portion 102 b, and travel back up towards thetop surface 106 t of the second portion 106 b of the isolation structure106. Due to constructive and/or destructive interference, only a coloredlight having a first wavelength that is associated with the secondthickness t₂ of the second portion 106 b of the isolation structure 106will be emitted/visible from a top surface of the optical emitterstructure 110 in the second pixel region 101 b.

Similarly, in the third pixel region 101 c, the exemplary second lightpath 204 shows how in some embodiments, the generated light at the firstinterface 206 may reflect off of the top surface 106 t of the thirdportion 106 c of the isolation structure 106 and/or travel through thethird portion 106 c of the isolation structure 106, reflect off of thethird reflector electrode portion 102 c, and travel back up towards thetop surface 106 t of the third portion 106 c of the isolation structure106. Due to constructive and/or destructive interference, only a coloredlight having a second wavelength that is associated with the thirdthickness t₃ of the third portion 106 c of the isolation structure 106will be emitted/visible from a top surface of the optical emitterstructure 110 in the third pixel region 101 c. In some embodiments,because the third thickness t₃ of the third portion 106 c of theisolation structure 106 being different than the second thickness t₂ ofthe second portion 106 b of the isolation structure 106, the secondwavelength will be different from the first wavelength, and thus, thethird pixel region 101 c emits a different colored light than the secondpixel region 101 b. Thus, the control circuitry 120 may use digital datato selectively turn “ON” one or more of the pixel regions (e.g., 101 a,101 b, 101 c) to produce an optical image.

FIGS. 3-13 illustrate cross-sectional views 300-1300 of some embodimentsof a method of forming a via structure over an isolation structure for adisplay device, the via structure having a protective layer to preventdamage to the isolation structure. Although FIGS. 3-13 are described inrelation to a method, it will be appreciated that the structuresdisclosed in FIGS. 3-13 are not limited to such a method, but insteadmay stand alone as structures independent of the method.

As shown in the cross-sectional view 300 of FIG. 3, a reflectorelectrode 102 may be formed over control circuitry 120. In someembodiments, the control circuitry 120 may comprise an interconnectstructure 130 arranged over a substrate 122. The interconnect structure130 may comprise interconnect wires 134 and interconnect vias 136embedded in an interconnect dielectric structure 132. In someembodiments, the interconnect wires and vias 134, 136 may comprisecopper, tungsten, or the like. The interconnect structure 130 may couplethe reflector electrode 102 to semiconductor devices 124 integrated onthe substrate 122. In some embodiments, the semiconductor devices 124may be or comprise metal oxide semiconductor field-effect transistors(MOSFETs), wherein the MOSFETs comprise source/drain regions 124 a inthe substrate 122. The semiconductor devices 124 may further comprise agate electrode 124 b arranged over a gate dielectric layer 124 c on thesubstrate 122. In alternative embodiments, the reflector electrode 102may be formed over a carrier substrate, and then the reflector electrode102 is later removed from the carrier substrate and bonded to controlcircuitry (120 of FIG. 1A) after the formation of pixel regions (e.g.,101 a, 101 b, 101 c of FIG. 1A).

In some embodiments, the reflector electrode 102 may be separated byfirst barrier structures 104 such that the reflector electrode 102 has afirst reflector electrode portion 102 a, a second reflector electrodeportion 102 b, and a third reflector electrode portion 102 c, forexample. In some embodiments, the first barrier structures 104 comprisethe same material as the interconnect dielectric structure 132. Thereflector electrode 102 may comprise a metal that is both electricallyconductive and optically reflective. For example, in some embodiments,the reflector electrode 102 may comprise aluminum or aluminum copper. Insome embodiments, the first barrier structures 104 may be formed using adeposition process (e.g., physical vapor deposition (PVD), chemicalvapor deposition (CVD), PE-CVD, atomic layer deposition (ALD),sputtering, etc.) followed by a patterning process (e.g.,photolithography and etching). The reflector electrode 102 may then beformed over the interconnect dielectric structure 132 using a depositionprocess (e.g., physical vapor deposition (PVD), chemical vapordeposition (CVD), PE-CVD, atomic layer deposition (ALD), sputtering,etc.) followed by a patterning process (e.g., photolithography, etching,chemical mechanical planarization (CMP), etc.).

Further, an isolation structure 106 is formed over the reflectorelectrode 102. In some embodiments, the isolation structure 106comprises a first portion 106 a, a second portion 106 b, and a thirdportion 106 c having a first thickness t₁, a second thickness t₂, and athird thickness t₃, respectively. The thicknesses (t₁, t₂, t₃) may bedetermined based the material of the isolation structure 106 and apredetermined light color to be emitted from each portion (106 a, 106 b,106 c) of the isolation structure 106. In some embodiments, theisolation structure 106 comprises a material that has opticalproperties, such that incident light may reflect as a colored light dueto constructive and/or destructive interference, and wherein the colorof the colored light is dependent on the thickness of the isolationstructure 106. Non-limiting examples of such a material include siliconnitride and silicon dioxide. Further, each portion (106 a, 106 b, 106 c)of the isolation structure 106 may be continuously connected to oneanother. In some embodiments, the formation of the isolation structure106 may comprise steps of deposition processes (e.g., physical vapordeposition (PVD), chemical vapor deposition (CVD), PE-CVD, atomic layerdeposition (ALD), sputtering, etc.) and patterning processes (e.g.,photolithography/etching processes). In some embodiments, the firstbarrier structures 104 comprise the same material as the isolationstructure 106. Further in some embodiments, the first barrier structures104, the interconnect dielectric structure 132, and the isolationstructure 106 comprise a same material. In other embodiments, the firstbarrier structures 104 and/or the interconnect dielectric structure 132may comprise a dielectric material such as undoped silicate glass (USG),silicon nitride, or like. In some embodiments, the first, second, andthird thicknesses t₁, t₂, t₃ of the isolation structure 106 may each bein a range of between, for example, approximately 200 angstroms andapproximately 1500 angstroms.

As shown in the cross-sectional view 400 of FIG. 4, in some embodiments,a conformal protective layer 402 is deposited over the isolationstructure 106. In some embodiments, the conformal protective layer 402has a seventh thickness t₇ in a range of between, for example,approximately 100 angstroms and approximately 300 angstroms. Theconformal protective layer 402 may be deposited by a deposition process(e.g., physical vapor deposition (PVD), chemical vapor deposition (CVD),PE-CVD, atomic layer deposition (ALD), sputtering, etc.). In someembodiments, the conformal protective layer 402 may comprise aconductive metal, such as, for example, titanium nitride or tantalumnitride. In alternative embodiments, the conformal protective layer 402may instead be a conformal dielectric layer. The conformal protectivelayer 402 comprises a material resist or to a cleaning process (see, 702of FIG. 7) later used. Similarly, the seventh thickness t₇ of theconformal protective layer 402 is thick enough to prevent the cleaningprocess (see, 702 of FIG. 7) from causing the top surfaces 106 t of theisolation structure 106 to become exposed during the cleaning process(see, 702 of FIG. 7) later used.

As shown in the cross-sectional view 500 of FIG. 5, in some embodiments,a first masking layer 502 may be formed over the conformal protectivelayer 402. The first masking layer 502 may comprise first openings 504.In some embodiments, each of the first openings 504 may be arranged overeach portion (106 a, 106 b, 106 c) of the isolation structure 106. Insome embodiments, the first masking layer 502 may be formed byphotolithography and may comprise a photosensitive material (e.g.,photoresist) formed by a spin coating process. In such embodiments, thelayer of photosensitive material is selectively exposed toelectromagnetic radiation according to a photomask or photoreticle. Theelectromagnetic radiation modifies a solubility of exposed regionswithin the photosensitive material to define soluble regions. Thephotosensitive material is subsequently developed to define the firstopenings 504 within the photosensitive material by removing the solubleregions. In other embodiments, the first masking layer 502 may comprisea hard mask layer (e.g., a silicon nitride layer, a silicon carbidelayer, or the like) patterned by, for example, aphotolithography/etching process or some other suitable patterningprocess.

As shown in the cross-sectional view 600 of FIG. 6, a first etchingprocess 602 may be performed to remove portions of the conformalprotective layer 402 and the isolation structure 106 underlying thefirst openings (504 of FIG. 5) of the first masking layer 502, therebyforming second openings 604 in the isolation structure 106. In someembodiments, the second openings 604 have a fourth width w₄ in a rangeof between, for example, approximately 0.1 micrometers and approximately0.6 micrometers. Bottoms of the second openings 604 may be defined byfirst surfaces 606 of the reflector electrode 102, and sidewalls of thesecond openings 604 may be defined by inner sidewalls 106 s of theisolation structure 106. In some embodiments, the first etching process602 is a dry etching process, and residue 608 is left behind on thefirst surfaces 606 of the reflector electrode 102. The residue maycomprise, for example, a metal oxide, comprising material of theisolation structure 106, the reflector electrode 102, and/or theconformal protective layer 402.

As shown in the cross-sectional view 700 of FIG. 7, the first maskinglayer (502 of FIG. 6) may be removed, and a cleaning process 702 may beperformed over the isolation structure 106 to remove the residue (608 ofFIG. 6) on the first surfaces 606 of the reflector electrode 102. Insome embodiments, the cleaning process 702 may be or comprise an argonsputtering process. Further, in such embodiments, during the cleaningprocess 702, top surfaces 106 t of the isolation structure 106 arecovered by the conformal protective layer 402. Thus, the top surfaces106 t of the isolation structure 106 are protected by the conformalprotective layer 402 and damage to the isolation structure 106 by thecleaning process 702 is prevented. Because the top surfaces 106 t areused for the reflection of light (see, FIG. 2) during the operation ofthe display device, the prevention of damage (e.g., an increase insurface roughness, change in composition, etc.) to the top surfaces 106t of the isolation structure is important for a reliable display device.Thus, before the cleaning process 702 (e.g., FIG. 6), the isolationstructure 106 may have top surfaces 106 t having a first average surfaceroughness, and after the cleaning process 702, the top surfaces 106 tmay have a second average surface roughness that is the same as thefirst average surface roughness because of the conformal protectivelayer 402. In some embodiments, to measure average surface roughness, aroughness measurement tool (e.g., a profilometer, AFM) calculates a meanline along a surface and measures the deviation between the height of apeak or valley on the surface from the mean line. After measuring manydeviations at many peaks and valleys throughout the surface, the averagesurface roughness is calculated by taking the mean of the manydeviations, where the deviations are absolute values. In otherembodiments, the surface roughness is quantified by measuring a totalthickness variation (TTV). The TTV of a layer is the difference betweenthe smallest thickness and the largest thickness of the layer. The TTVis measured throughout the length of a layer.

As shown in the cross-sectional view 800 of FIG. 8, a conformalconductive layer 802 may be deposited over the conformal protectivelayer 402 and along the sidewalls and bottoms of the second openings(604 of FIG. 7). In some embodiments, the conformal conductive layer 802has a fourth thickness t₄ in a range of between, for example,approximately 200 angstroms and approximately 700 angstroms. In otherembodiments, the fourth thickness t₄ may be in a range of between, forexample, approximately 100 angstroms and approximately 900 angstroms. Insome embodiments, the fourth thickness t₄ is greater than the sevenththickness t₇ of the conformal protective layer 402, whereas in otherembodiments, the fourth thickness t₄ may be less than or about equal tothe seventh thickness t₇. Further, the conformal conductive layer 802may not fill in the second openings (604 of FIG. 7), and thus, thirdopenings 804 may remain between the inner sidewalls 106 s of theisolation structure 106. In other words, two times the fourth thicknesst₄ is less than the fourth width (w₄ of FIG. 6) of the second openings(604 of FIG. 7). In alternative embodiments, the conformal conductivelayer 802 may completely fill the second openings (604 of FIG. 7), suchthat the third openings 804 are not present. (see, 108 of FIG. 2). Thus,in alternative embodiments, the fourth thickness t₄ may be greater thanhalf of the fourth width (w₄ of FIG. 6) of the second openings (604 ofFIG. 7). In such alternative embodiments, the conformal conductive layer802 may have upper surfaces with small indents that overlie the firstsurface 606 of the reflector electrode 102.

Further, in some embodiments, the conformal conductive layer 802 maycomprise a conductive metal, such as, for example, titanium nitride ortantalum nitride. Thus, in some embodiments, the conformal protectivelayer 402 and the conformal conductive layers 802 comprise a samematerial. In other embodiments, the conformal conductive layer 802 maycomprise a different material than the conformal protective layer 402.The conformal conductive layer 802 may directly contact the firstsurface 606 of the reflector electrode 102 because of the removal ofresidue (608 of FIG. 8) by the cleaning process (702 of FIG. 7). Thedirect contact between the conformal conductive layer 802 and thereflector electrode 102 allows for a reliable electrical connection. Theconformal conductive layer 802 may be deposited by a deposition process(e.g., physical vapor deposition (PVD), chemical vapor deposition (CVD),PE-CVD, atomic layer deposition (ALD), sputtering, etc.).

As shown in the cross-sectional view 900 of FIG. 9, a second maskinglayer 902 is formed over the conformal conductive layer 802 and withinthe third openings (804 of FIG. 8). The second masking layer 902 mayoverlie portions of top surfaces 802 t of the conformal conductive layer802. It will be appreciated that second masking layer may be formed by asimilar photolithography process as used for the first masking layer 502in FIG. 5.

As shown in the cross-sectional view 1000 of FIG. 10, a second etchingprocess 1002 may be performed to remove peripheral portions of theconformal protective layer (402 of FIG. 9) and the conformal conductivelayer (802 of FIG. 9) according to the second masking layer 902 to formvia structures 108. The via structures 108 may comprise a protectivelayer 108 a and a conductive layer 108 b. In some embodiments, thesecond etching process 1002 comprises a wet etching process instead of adry etching process to mitigate residual damage to the top surfaces 106t of the isolation structure 106 upon removal of the conformalprotective layer (402 of FIG. 9). Thus, the second etching process 1002may use a wet etchant that does not affect the isolation structure 106.Further, in some embodiments, after the second etching process 1002, thetop surfaces 106 t of the isolation structure 106 that are uncovered bythe protective layer 108 a may have a third average surface roughnessthat is about equal to the second surface roughness.

As shown in the cross-sectional view 1100 of FIG. 11, the second maskinglayer (902 of FIG. 10) is removed. The via structures 108 each comprisean upper horizontal segment 108 u comprising the protective layer 108 aand the conductive layer 108 b, whereas the via structures 108 maycomprise a sidewall vertical segment 108 s and a center horizontalsegment 108 c that comprise only the conductive layer 108 b. In someembodiments, the upper horizontal segment 108 u of the via structures108 has a fifth thickness t₅ that is greater than the fourth thicknesst₄ of the center horizontal segment 108 c and a sixth thickness t₆ ofthe sidewall vertical segment 108 s. In some embodiments, the differencebetween the fifth thickness t₅ and the fourth thickness t₄ is aboutequal to the seventh thickness (t₇ of FIG. 4) of the conductive layer108 b. In some embodiments, the fifth thickness t₅ is in a range ofbetween approximately 300 angstroms and approximately 1000 angstroms,for example.

As shown in the cross-sectional view 1200 of FIG. 12, a transparentelectrode 112, optical emitter structure 110, and second barrierstructures 114 are formed over the isolation structure 106 and viastructures 108. In some embodiments, the transparent electrode 112 hasbottommost surfaces 112 b that are below the top surfaces 106 t of theisolation structure 106 because the transparent electrode 112 fills thethird openings (804 of FIG. 8) of the via structures 108. Thus, from thecross-sectional view 1200, the via structures 108 each have two sidewallvertical segments (108 s of FIG. 11) separated from one another by thetransparent electrode 112. Further, the via structures 108 electricallycouple the transparent electrode 112 to the reflector electrode 102. Insome embodiments, the transparent electrode 112 may comprise anelectrically conductive material that is also optically transparent,such as, for example, indium tin oxide (ITO), fluorine tin oxide (FTO),or the like. In some embodiments, the transparent electrode 112 may havea thickness that is, for example, in a range of between approximately500 angstroms and approximately 3000 angstroms. In some embodiments, theoptical emitter structure 110 may be or comprise an organic lightemitting diode (OLED) or some other suitable light generating device. Insome embodiments, the optical emitter structure 110 may have a thicknessin the range of between, for example, approximately 500 angstroms andapproximately 3000 angstroms.

In some embodiments, in order to generate light at a first interface 206between the transparent electrode 112 and the optical emitter structure110 during operation of the display device, the transparent electrode112 and the optical emitter structure 110 may comprise differentmaterials. Further, in some embodiments, the second barrier structures114 may separate portions of the transparent electrode 112 and theoptical emitter structure 110 to define a first pixel region 101 a, asecond pixel region 101 b, and a third pixel region 101 c. It will beappreciated that the display device may comprise an array of pixelregions, and may comprise more than the first, second, and third pixelregions 101 a, 101 b, 101 c. Some of the second barrier structures 114may directly overlie the first barrier structures 104, and the secondbarrier structures 114 may comprise a dielectric material toelectrically and optically isolate the pixel regions (101 a, 101 b, 101c) from one another. For example, the second barrier structures 114 maycomprise a nitride (e.g., silicon nitride, silicon oxynitride), an oxide(e.g., silicon oxide), or the like. For example, in some embodiments,the second barrier structures 114 may comprise a multi-layer film stackof silicon nitride and silicon oxide. Further, in some embodiments, thesecond barrier structures 114 may comprise a same material as theisolation structure 106, the first barrier structures 104, and/or theinterconnect dielectric structure 132. The transparent electrode 112,the optical emitter structure 110 and the second barrier structures 114may each be formed through various steps comprising deposition processes(e.g., physical vapor deposition (PVD), chemical vapor deposition (CVD),PE-CVD, atomic layer deposition (ALD), sputtering, etc.), removalprocesses (e.g., wet etching, dry etching, chemical mechanicalplanarization (CMP), etc.), and/or patterning processes (e.g.,photolithography/etching).

Thus, the display device comprises control circuitry 120 to selectivelyoperate the first, second, and third pixel regions 101 a, 101 b, 101 c.Because the protective layer 108 a that protected the isolationstructure 106 from damage by the cleaning process (702 of FIG. 7), eachof the pixel regions (101 a, 101 b, 101 c) may be selectively operatedby the control circuitry 120 to reliably emit colored light depending onthe thicknesses (t₁, t₂, t₃) of the isolation structure 106.

FIG. 13 illustrates a flow diagram of some embodiments of a method 1300corresponding to FIGS. 3-12.

While method 1300 is illustrated and described below as a series of actsor events, it will be appreciated that the illustrated ordering of suchacts or events are not to be interpreted in a limiting sense. Forexample, some acts may occur in different orders and/or concurrentlywith other acts or events apart from those illustrated and/or describedherein. In addition, not all illustrated acts may be required toimplement one or more aspects or embodiments of the description herein.Further, one or more of the acts depicted herein may be carried out inone or more separate acts and/or phases.

At act 1302, an isolation structure is formed over a reflectorelectrode. FIG. 3 illustrates cross-sectional view 300 of someembodiments corresponding to act 1302.

At act 1304, a protective layer is deposited over the isolationstructure. FIG. 4 illustrates cross-sectional view 400 of someembodiments corresponding to act 1304.

At act 1306, a first etching process is performed to form a firstopening in the protective layer and the isolation structure to expose afirst surface of the reflector electrode. FIGS. 5 and 6 illustratecross-sectional views 500 and 600 of some embodiments corresponding toact 1306.

At act 1308, a cleaning process is performed to clean the first surfaceof the reflector electrode. FIG. 7 illustrates cross-sectional view 700of some embodiments corresponding to act 1308.

At act 1310, a conductive layer is deposited over the protective layerand within the first opening. FIG. 8 illustrates cross-sectional view800 of some embodiments corresponding to act 1310.

At act 1312, peripheral portions of the protective layer and theconductive layer are removed to form a via structure within the opening,wherein the via structure comprises the protective layer and theconductive layer and extends from a top of the isolation structure tothe first surface of the reflector electrode. FIGS. 9-11 illustratecross-sectional views 900-1100 of some embodiments corresponding to act1312.

At act 1314, a transparent electrode is formed over the isolationstructure and the via structure.

At act 1316, an optical emitter structure is formed over the transparentelectrode. FIG. 12 illustrates cross-sectional view 1200 of someembodiments corresponding to acts 1314 and 1316.

Therefore, the present disclosure relates to a method of manufacturing avia structure using a protective layer and a conductive layer over anisolation structure to mitigate damage to the isolation structure,thereby producing a reliable display device.

Accordingly, in some embodiments, the present disclosure relates todisplay device comprising: an isolation structure disposed over areflector electrode; a transparent electrode disposed over the isolationstructure; an optical emitter structure disposed over the transparentelectrode; and a via structure extending from the transparent electrodeat a top surface of the isolation structure to a top surface of thereflector electrode, wherein the via structure comprises a centerhorizontal segment contacting the top surface of the reflectorelectrode, a sidewall vertical segment contacting an inner sidewall ofthe isolation structure, and an upper horizontal segment contacting thetop surface of the isolation structure, wherein the upper horizontalsegment is connected to the center horizontal segment by the sidewallvertical segment, and wherein the upper horizontal segment is thickerthan the center horizontal segment.

In other embodiments, the present disclosure relates to a display devicecomprising: a reflector electrode coupled to an interconnect structure;an isolation structure disposed over the reflector electrode; atransparent electrode disposed over the isolation structure; an opticalemitter structure disposed over the transparent electrode; and a viastructure extending from a top surface of the isolation structure to thereflector electrode, wherein the via structure comprises a first layeron the top surface of the isolation structure and further comprises asecond layer, wherein the second layer overhangs the top surface of theisolation structure and is spaced from the top surface of the isolationstructure by the first layer, and wherein the second layer has adownward protrusion directly contacting the reflector electrode and aninner sidewall of the isolation structure.

In yet other embodiments, the present disclosure relates to a method offorming a display device, the method comprising: forming an isolationstructure over a reflector electrode; depositing a protective layer overthe isolation structure; forming a first opening extending through theprotective layer and the isolation structure to expose a first surfaceof the reflector electrode, wherein inner sidewalls of the protectivelayer and the isolation structure define sidewalls of the first opening;performing a cleaning process to clean the first surface of thereflector electrode; depositing a conductive layer over the protectivelayer, the sidewalls of the first opening, and the first surface of thereflector electrode; and performing an etching process to removeperipheral portions of the protective layer and the conductive layer toform a via structure comprising the protective layer and the conductivelayer, wherein the via structure directly contacts and extends from atop surface of the isolation structure to the first surface of thereflector electrode.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A display device comprising: an isolationstructure disposed over a reflector electrode; a transparent electrodedisposed over the isolation structure; an optical emitter structuredisposed over the transparent electrode; and a via structure extendingfrom the transparent electrode at a top surface of the isolationstructure to a top surface of the reflector electrode, wherein the viastructure comprises a center horizontal segment contacting the topsurface of the reflector electrode, a sidewall vertical segmentcontacting an inner sidewall of the isolation structure, and an upperhorizontal segment contacting the top surface of the isolationstructure, wherein the upper horizontal segment is connected to thecenter horizontal segment by the sidewall vertical segment, and whereinthe upper horizontal segment is thicker than the center horizontalsegment.
 2. The display device of claim 1, wherein the transparentelectrode has a protrusion protruding into the via structure to thecenter horizontal segment, and wherein the via structure cups anunderside of the protrusion.
 3. The display device of claim 1, whereinthe upper horizontal segment of the via structure comprises a conductivelayer over a protective layer.
 4. The display device of claim 1, whereinthe via structure comprises titanium nitride.
 5. The display device ofclaim 1, wherein the sidewall vertical segment and the center horizontalsegment comprise a continuous layer of a single material.
 6. The displaydevice of claim 1, wherein a first thickness of each of the upperhorizontal segment is measured in a first direction normal to the topsurface of the reflector electrode, and wherein a second thickness ofthe center horizontal segment is measured in the first direction.
 7. Thedisplay device of claim 6, wherein the sidewall vertical segment has athird thickness measured in a second direction that is perpendicular tothe first direction, and wherein the first thickness is greater than thethird thickness.
 8. A display device comprising: a reflector electrodecoupled to an interconnect structure; an isolation structure disposedover the reflector electrode; a transparent electrode disposed over theisolation structure; an optical emitter structure disposed over thetransparent electrode; and a via structure extending from a top surfaceof the isolation structure to the reflector electrode, wherein the viastructure comprises a first layer on the top surface of the isolationstructure and further comprises a second layer, wherein the second layeroverhangs the top surface of the isolation structure and is spaced fromthe top surface of the isolation structure by the first layer, andwherein the second layer has a downward protrusion directly contactingthe reflector electrode and an inner sidewall of the isolationstructure.
 9. The display device of claim 8, wherein the top surface ofthe isolation structure has a first portion that directly contacts thevia structure and a second portion that directly contacts thetransparent electrode, wherein the first portion of the top surface ofthe isolation structure has a first average surface roughness, whereinthe second portion of the top surface of the isolation structure has asecond average surface roughness, wherein the first average surfaceroughness is about equal to the second average surface roughness. 10.The display device of claim 8, wherein the first layer comprises adifferent material than the second layer.
 11. The display device ofclaim 8, wherein the via structure has a first thickness measured fromthe top surface of the isolation structure to a topmost surface of thevia structure, wherein the via structure has a second thickness measuredfrom a bottommost surface of the via structure to a bottommost surfaceof the transparent electrode, and wherein the first thickness is greaterthan the second thickness.
 12. The display device of claim 11, whereinthe via structure directly contacts an inner sidewall of the transparentelectrode, wherein the via structure directly separates the innersidewall of the isolation structure and the inner sidewall of thetransparent electrode, wherein the via structure has a third thicknessmeasured from the inner sidewall of the transparent electrode to theinner sidewall of the isolation structure, and wherein the firstthickness is greater than the third thickness, and wherein the thirdthickness is about equal to the second thickness.
 13. The display deviceof claim 11, wherein the first thickness is at least about 100 angstromsgreater than the second thickness.
 14. A display device comprising: afirst pixel region arranged over a substrate and comprising: a firstisolation structure disposed over a first reflector electrode, a firsttransparent electrode disposed over the first isolation structure, afirst optical emitter structure disposed over the first transparentelectrode, and a first via structure extending from a topmost surface ofthe first isolation structure to the first reflector electrode, whereinthe first via structure comprises a first layer on the topmost surfaceof the first isolation structure and a second layer arranged over thefirst layer, and wherein the second layer has a downward protrusiondirectly contacting the first reflector electrode and an inner sidewallof the first isolation structure; and a second pixel region arrangedover the substrate, laterally beside the first pixel region, andcomprising: a second isolation structure disposed over a secondreflector electrode, a second transparent electrode disposed over thesecond isolation structure, a second optical emitter structure disposedover the second transparent electrode, and a second via structureextending from a topmost surface of the second isolation structure tothe second reflector electrode, wherein the second via structurecomprises a third layer on the topmost surface of the second isolationstructure and a fourth layer arranged over the third layer, and whereinthe fourth layer has a downward protrusion directly contacting thesecond reflector electrode and an inner sidewall of the second isolationstructure.
 15. The display device of claim 14, wherein the first andthird layers of the first and second via structures, respectively,comprise a dielectric material, and wherein the second and fourth layersof the first and second via structures, respectively, comprise aconductive material.
 16. The display device of claim 14, wherein thefirst and third layers of the first and second via structures,respectively, comprise a first conductive material, and wherein thesecond and fourth layers of the first and second via structures,respectively, comprise a second conductive material different than thefirst conductive material.
 17. The display device of claim 14, furthercomprising: a barrier structure arranged over the first isolationstructure and the second isolation structure and arranged directlybetween the first optical emitter structure and the second opticalemitter structure, wherein the first isolation structure directlycontacts the second isolation structure.
 18. The display device of claim14, wherein a bottommost surface of the first transparent electrode isarranged below the topmost surface of the first isolation structure, andwherein a bottommost surface of the second transparent electrode isarranged below the topmost surface of the second isolation structure.19. The display device of claim 14, wherein the first isolationstructure has a first thickness measured between the topmost surface anda bottommost surface of the first isolation structure, wherein thesecond isolation structure has a second thickness measured between thetopmost surface and a bottommost surface of the second isolationstructure, and wherein the second thickness is less than the firstthickness.
 20. The display device of claim 19, wherein the first viastructure has a third thickness measured between a topmost surface and abottommost surface of the first via structure, wherein the second viastructure has a fourth thickness measured between a topmost surface anda bottommost surface of the second via structure, and wherein the fourththickness is less than the third thickness.